Analysis Framework for the Evaluation of Media Beds in the Orion Smoke Eater Filter

In the event of a fire onboard the Orion Multi-Purpose Crew Vehicle (MPCV), the Orion Smoke Eater Filter (OSEF) will be used to clean the cabin atmosphere via removal of particulates and potentially harmful gases. To facilitate this, the OSEF contains a bed of impregnated activated carbon to remove hydrocarbons, acid gases, and NH3 and a supported catalyst bed to oxidize CO to CO2. The analyses described herein were motivated by computerized tomography (CT) scans of an OSEF build and the packed beds of a similar technology which found potential channel formation and breakdown of the catalyst materials. In this work, we examined the potential adverse effects of these anomalies in bed packing. A model was generated to calculate the scrubbing rate of CO in the cabin. Next, the influence of channeling in the catalyst bed was examined; the Fanning and Colebrook equations were used to determine the amount of flow bypassing the catalyst bed due to the presence of channels and the size and number of channels allowable for appropriate scrubbing of the cabin. When the catalyst support in the CO catalyst bed breaks down, dusting occurs, affecting the flow across the particle bed and thereby reducing the catalyst bed utilization. We determined the effects of dusting on the scrubbing time using the scrubbing model and its impact on the pressure differential via a modified form of the Ergun equation; based on these analyses, requirements for the maximum allowable dusting concentrations were derived. The procedures and results described herein provide a framework for future examinations of the efficacy of bed packing procedures and the influence that they may have on contaminant removal applications.